1. Field of the Invention
This invention relates generally to Emitter Locator Systems and, more specifically, to a Direction Finding Method and System Using Probabilistic Mapping.
2. Description of Related Art
Emitter Location (EL) Systems are used to locate the position of emitting radio transmitters. Typically, once an EL System determines where (to the best of its ability) a transmitter is, this location is then plotted on a relevant map display for the operator. Other systems or modes sometimes only display the relative bearing from the receiver to the transmitter, where a radio Direction Finding (DF) System is employed. Unfortunately, real-world EL System measurements inherently have uncertainties due to several factors. Thus, the position of a transmitter on a display is only accurate to within a certain measurement error.
Some of today's EL systems display the error as a fixed offset shown on the screen using two lines to draw a “wedge” of a reading, say from 275 to 285 degrees. Other systems display the expected error on a separate indicator (as a number, or as a bar graph of varying height or length), and then the operator is expected to apply this expected error to the reading. Yet another group of EL systems does not display the error at all. This leaves the EL System operator with an inherently imprecise location of the transmitter, and thus a decreased confidence and reliability in the position “fix.”
The invention of this disclosure is a computer-executed display system and method that provides a far more useful, practical, and probabilistic method of presenting measurement data to EL System operators than is presently done today. This is done by a unique display method and system that takes measurements, produces and displays “probability fields” related to where a transmitter is most likely to be located. The fields change interactively in real-time and are constantly updated as new measurements arrive. In addition, the method of this display system performs statistical calculations to further enhance the accuracy of the probability presentations.
To understand how this invention provides a unique probabilistic display of an emitter's location, it is first important to understand the technique by which EL Systems are employed.
An EL System may be comprised of one or more radio Direction Finding (DF) “Sets” which can either be fixed in location, or mobile on a vehicle, ship, aircraft, etc. The invention of this disclosure relates to EL Systems employing at least one mobile DF Set.
The invention uses an improved technique to collect data from one or multiple DF Sets, and then to intelligently present that data so that overall measurement uncertainties are included as part of the display. Since this unique display presents an intelligent probabilistic location of the transmitter, the odds that an EL System operator will actually locate that transmitter are greatly increased.
In conclusion, insofar as the inventor is aware, no invention formerly developed provides this unique method of probabilistically displaying transmitter locations in emitter location systems.